Laundry detergent compositions containing soil release polymers, which assist the release of soil from fabrics during the laundry process, have been widely disclosed in the art.
Polyesters of terephthalic and other aromatic dicarboxylic acids, in particular, the so-called PET/POET (polyethylene terephthalate/polyoxyethylene terephthalate) and PET/PEG (polyethylene terephthalate/polyethylene glycol) polyesters, are known to have soil release properties. Such polyesters are disclosed, for example, in U.S. Pat. No. 3,557,039 (ICI), GB 1 467 098, EP 1305A and EP 271 312B (Procter & Gamble). Sulphonated polyesters having soil release properties are disclosed in EP 874 892A, EP 977 827A, EP 1 019 476A, and EP 1 012 512A (Unilever).
The mechanism of action for many soil release polymers is that a polymeric layer is deposited on the fibres and modifies their surface so that subsequent soiling is deposited on and adheres to the polymeric layer rather than the fibres themselves. Removal of the soil during the next wash is thus greatly facilitated. Alternatively some polymers may assist release of soil directly from the fibres.
While improved release of soil from synthetic fabrics such as polyester has been successfully achieved, especially with the so-called PET/POET type of polymer, the effective release of soils, especially oily soils, from cotton has proved much more difficult.
WO 97 42285A discloses soil release polymers for cotton comprising a polyamine backbone and quaternary ammonium cationic groups. While substantivity to cotton is good, these materials have been found to give some negatives, notably staining of the laundered fabrics. The presence of anionic surfactants also interferes with the action of the polymers because of their high density of positive charge.
There remains a need in the art to identify soil release polymers that give good substantivity to cotton without other detrimental properties.